Nosocomial (hospital acquired) infections are the fourth leading cause of death in the U.S. with 2 million cases and more than $5 billion in added medical cost per annum. Each year approximately 10% of all patients admitted to hospitals in the U.S will develop a health-care associated infection, which translates to 2-4 million nosocomial infections, representing the eighth leading cause of death in the US, accounting for approximately 50,000 deaths annually. Other infections, such as those in the burns and wounds, also add significant morbidity and costs. Antibiotic therapy remains the mainstay for the treatment of infection; however, its success is severely threatened by the increasingly frequent development of resistance and the emergence of new microorganisms for which effective antibiotic therapies simply do not exist. To make matters worse, the antibiotic pipeline in most major pharmaceutical companies is drying up. One of the impediments to the rapid development of newer antibiotics is the fact that classical microbiological culture techniques are not compatible with modern methodologies for drug discovery that are dominated by high throughput screening (HTS) and its “hunger for speed”.
A large number of these nosocomial infections are fungal infections, and are often associated with implantable devices, intravascular and urinary catheters, orthopedic implants, and intrauterine contraceptive devices, which is an $180 b per year industry. Fungal infections can be lethal as seen by mortality rates—50% for candidiasis, 90% for aspergillosis, and 100% for zygomycosis. For example, in pediatric patients, candidiasis (the most common fungal infection) is associated with a 10.0% increase in mortality, a mean 21.1-day increase in length of stay, and a mean increase in total per-patient hospital charges of $92,266. Similarly, in adult patients candidiasis is associated with a 14.5% increase in mortality, a mean 10.1-day increase in length of stay, and a mean increase in hospital charges of $39,331. Overall, these numbers suggests that despite having a market of $3.1b per year, which is ˜10% of all anti-infectives, currently used antifungals are still ineffective. There are no new effective drugs in sight, and the antifungal pipeline is mostly dry. One of the reasons for poor efficacy of antifungal treatments is that many fungal organisms grow as ‘biofilms’ on surfaces of implantable medical devices, and the biofilms are significantly less susceptible to antifungal drugs compared to free-floating or planktonic cells. Biofilm infections are notoriously difficult to treat, and they commonly manifest as chronic or recurrent infections, and constitute a number of clinical challenges
Evidence also shows that a large percentage of these hospital acquired infections are polymicrobial in nature. Many such mixed microbial infections also involve the formation of microbial biofilms. Biofilms are complex three-dimensional structures, which are composed of different morphological forms of the microbial organism including yeast, pseudohyphae and hyphae, in an extracellular matrix. The antifungal/antibacterial resistance of biofilms is primarily attributed to changes in genetic, physiological and molecular characteristics of the cells in the biofilm, and secondarily to slow diffusion of drugs, and the binding of drugs to the biofilm matrix. Thus, there is a need to develop new strategies for the screening and discovery of antimicrobial drugs (antifungals, antibacterials, antivirals, mixed anti-microbials, etc.) that prevent or control the growth of microbial organisms and/or the formation of biofilms.
The current industry standard is a 96-well plate assay, which, when invented in 2001 was revolutionary and it changed the way fungal biofilms were examined. Prior to 2001, growth and characterization of fungal biofilms was an ordeal and was performed by only a handful of investigators primarily by forming one biofilm at a time. However, practical considerations of time, cost and reagent volume severely limit the use of 96-well plate assays for probing diverse set of chemical libraries containing tens of thousands of molecules for new drugs, and novel, innovative technologies are sorely needed.